The present invention relates to a seal and bleed valve unit for electric batteries.
It is known that inside batteries during operation and/or recharge, gases are generated because of the electrolysis and evaporation of water contained in the electrolytic solution that is known to be consisting of sulfuric acid and distilled water.
A particular kind of electric batteries are the so-called recombination batteries in which gases generated in operation are condensed inside the battery avoiding consumption of distilled water and the need to fill them up.
For safety reasons the recombination batteries are provided with a number of channels made in the cover closing the case containing the cells, said channels connecting the electrolytic cells of the battery with a safety valve unit allowing gas bleed to the outside when gas pressure exceeds a predetermined value.
Such a valve unit must also prevent inlet of air into the battery when on cooling temperature and consequently also pressure inside the battery are decreasing. A seal and bleed valve unit for electric batteries of the prior art is shown as an illustrative example in FIG. 1 where it is generally indicated with character A.
One can see that said unit comprises substantially a tubular neck B projecting from battery cover C and communicating with the inner room of the battery, an elastic cap generally indicated with D and consisting of a tubular body E closed by a bottom F being applied on said collar.
Cap D is shown also in FIGS. 2 and 3 where one can see that the cap is internally provided with three thinned portions G arranged at 120xc2x0 to each other, each portion being obtained by making part of the tubular body E and also of the bottom F thinner.
The end of the tubular body E at each thinned portion G has a lip H adhering to the tubular neck B to obtain a tight seal.
In the event of excess pressure inside the battery, the generated gas is discharged from inside to the outside through the duct I shown in FIG. 1 created between the tubular neck B and the thinned portion G, causing lip H to rise and therefore discharge of excess pressure to the external ambient.
On the contrary in the event of depression inside the battery, the external pressure forces lips H against the tubular neck B preventing entrance of air inside the battery.
A drawback of the above mentioned valve unit consists in that the small size of the thinned portions G and consequently of the ducts I created between cap and tubular neck B, makes difficult the discharge of excess pressure and the subsequent closure so as to increase inertia of the valve unit reacting rather slowly when pressure inside the battery increases or decreases. This may cause pressure to rise above the maximum admissible values.
Another drawback consists in that the sealing surface is limited only to the contact surface between the tubular body of the cap and the tubular neck and such a surface not always is sufficient to warrant tightness against entrance of air into the battery from the outside when the battery goes into depression.
The above mentioned drawbacks, namely the high inertia of the opening and closing operation to the outside and the limited tightness to the inside, are generally found in a more or less marked way in all the prior art valve units, even if they are constructed differently from the above illustrated and described valve unit.
The present invention aims at overcoming said drawbacks.
More particularly a first object of the invention is to provide a seal and bleed valve unit having an operation inertia when opening which is lower in comparison with equivalent known valve units.
Another object of the invention is a valve unit having a greater tightness when closed in comparison with equivalent known valve units.
Said objects are attained by a seal and bleed valve unit for electric batteries that according to the main claim comprises:
at least a tubular neck associated to the cover of said battery and adapted to put the external ambient in communication with the bleed ducts made in said cover;
an elastic cap consisting of a tubular body closed by a bottom, removably coupled to the outside of said tubular neck,
and is characterized in that said tubular neck ends with a thinner collar relative to the outer surface of said tubular neck, cooperating with the inner surface of said cap to define an annular chamber.
According to a preferred embodiment, the tubular neck is part of the battery cover being integral with said cover.
The collar made in the tubular neck is tapered with a frustum conical shape and the annular chamber is defined between the outer surface of the collar and the annular intersection zone determined by the contact between the inner surfaces of tubular body and bottom of the cap.
The valve unit is arranged inside a chamber made in the battery cover, said chamber being closed through a plug provided with holes constraining the cap when increase of inner pressure of the battery tends to detach the cap from the tubular neck to which it is coupled.
In the event of excess pressure inside the battery, the elastic cap rises from the tubular neck allowing gas discharge.
On the contrary in the event of battery depression, the atmospheric pressure greater than the inner pressure of the battery, causes the elastic cap to adhere to the tubular neck preventing entrance of air from outside.
According to a constructional variation the tubular neck is part of a plug applied to the battery cover. In this way the entire valve unit can be removed from the battery cover.
Advantageously the annular chamber between the collar of the tubular neck and the elastic cap, allows the pressurized gas generated inside the battery to push radially the tubular body of the cap on the entire circumference at the same time. This makes easier gas discharge to the outside and reduces operation inertia of the valve unit as a whole, so as to avoid dangerous increase of pressure inside the battery during operation.
Still advantageously the collar ensures tightness also against the bottom of the elastic cap, thus warranting a better tightness of the battery to the outside when it goes into depression.